The present invention relates generally to a lenslet array and more particularly to an improvement of the lenslet arrangement found in my copending application Ser. No. 912,688, filed June 5, 1978, now U.S. Pat. No. 4,185,191 my copending application Ser. No. 023,865, filed Mar. 26, 1979, and the copending application of Stauffer and Wilwerding, Ser. No. 16,595, filed Mar. 1, 1979 wherein lenslets are used in connection with distance determining or automatic focusing of, for example, photographic or television cameras.
In the above-mentioned copending application, radiation from a remote scene to be focused upon, is directed by an objective lens to a plurality of lenslets mounted proximate the image plane of the objective lens. Each lenslet produces an image of the exit pupil of the objective lens and proximate the image plane of each lenslet is mounted a pair of radiation sensitive detectors. Each detector produces an output indicative of the radiation it receives and when the objective lens is properly positioned in the desired focus position, the detectors in each pair will receive approximately the same amount of radiation. As the objective lens moves from a proper focus position, the output of the detectors becomes unequal. The inequality in outputs of the detectors is analyzed by a system to determine the direction the objective lens must be moved to attain a proper focus.
In the above copending application, the image produced by the lenslets is circular in nature or, if the lens is stopped down during the focussing operation, is the shape of the iris mechanism and this image changes in size as lenses of different f numbers are used or as the iris mechanism is opened and closed. To operate properly, the detectors must be placed within the periphery of the smallest of the images to be encountered and thus the detectors are restricted in size. It is desirable to have detectors of as large a surface area as possible so as to increase the outputs thereof but with the generally circular configuration of the image of the exit pupil of the objective lens and its varying size, the amount of surface area available for the detectors is reduced. The circular or spherical shape of the lenslets used in the arrays of the above-referred to copending application has, because of their very small size, been found difficult to manufacture in tiny arrays with good accuracy.